Field of the Invention
The present invention relates to door latch interlock mechanisms. More particularly, the present invention relates to door latch interlock mechanisms useful in conjunction with rigid containers having flexible liners for storing or processing liquids or other fluid materials.
Description of the Related Art
Storage and processing containers are in widespread use in various industries and other endeavors. Many of these are used to contain liquids and other flowable bulk materials, such as powders and granular materials. While containing many types of fluid materials, it is preferable to line the container with a polymeric membrane so that the bulk material is either impermeably contained in a suitable polymeric material, or to insure that the bulk materials does not contact the container itself. For example, in the case of pharmaceutical and food grade materials, a polymeric liner, such as PVC or polypropylene, may be used to maintain the purity and cleanliness of the bulk material. In other instances, the bulk material may react with a storage container itself, so a polymeric liner is used to prevent such reactions.
Even though such storage and process containers may be lined, it is still necessary to access the interior of cleaning and service. For this reason, such containers may be equipped with doors large enough for workers to access the interior. In fact, such doors may be the access port through which polymeric liners are installed. It is necessary to securely latch the doors in a closed position when they are not in use. Particularly when the container is filled with a fluid material since the static pressure produced under the force of gravity generates a substantial opening force against the interior of the door. Herein lies a risk of such designs. If the door were intentionally or inadvertently opened while the lined container was full of a fluid material, then the static pressure would push the liner outwardly through the door opening. In fact, the liner may rupture, allowing the fluid material to flow out of the container. Thus it can be appreciated that there is a need in the art for an apparatus for mitigating the potential risk of opening such a door while there is fluid in the process container.